A knife killer who sliced off his sister's nose and stabbed his best friend to death is bidding to overturn his murder conviction.

Michael John Robson was jailed for life at Newcastle Crown Court in October 1996 after being found guilty of killing pal Robert Williamson and wounding with intent.

During a nine-day trial, the prosecution said Robson plunged an eight-inch serrated kitchen knife into 27-year-old Mr Williamson's chest after an argument in Avon Drive, North Shields, in June the previous year.

The court heard Robson, formerly of Waterville Road, caused a fatal six-inch wound after using the knife on Williamson through the passenger window of his car.

The Crown claimed he was in a "violent and aggressive state" and was upset because Mr Williamson had previously taken a gun from him which he had intended to use to kill himself.

He then walked away and used the knife just minutes later in a row with his sister Lisa - who was 24 at the time -almost severing her nose.

The jury was told she spent one-and-a-half hours in the operating theatre and needed up to 30 stitches. Robson denied the two charges but was found guilty by the jury.

Now, nine years after his conviction, he is challenging the verdict. Initial legal arguments were heard at London's Appeal Court this week.

Lord Justice Gage said the 34-year-old would be granted legal representation at a future appeal hearing so the court can decide whether he should be allowed an extension of the normal time limit to pursue his challenge.

No date was fixed for the hearing of Robson's application, which is expected to centre on whether diminished responsibility made the murder conviction unsafe.

During the trial, his defence centred on provocation and diminished responsibility. Psychiatrists gave evidence Robson had a mental disorder which left him in emotional turmoil, impairing his ability to act responsibly.

The court heard he had suffered five years of family bereavements.

His mother Anne died from cancer in 1990 and, the following year, his brother Dale was killed in a car crash which sparked the Meadow Well riots.

In 1992, his nana Elizabeth Rutley died and on New Year's Eve 1995 his Uncle Matty was found hanged. Before the attacks, Robson was said to have been so depressed he prepared to kill himself with a shotgun at his home, Newcastle Crown Court was told. However, he was unable to commit suicide when he failed to find any bullets.

After the trial, his sister Lisa, 35, told how she had forgiven him for the attack which left her scarred for life.

She said: "When I heard the verdict it was like losing another brother.

"People think he's mad but I know he's not. When we lived together he was like my protector and in a way he still is. How could I not forgive him?"